Torsional isolator

ABSTRACT

A torsional isolator ( 200, 300, 400 ) designed to reduce vibrations and shock experienced by electronics used during directional drilling is disclosed. The torsional isolator allows the drillstring electronics to oscillate at a slower rotational velocity than the data acquisition rate of associated sensors, such that the sensors record an average value of the azimuth heading thereby allowing for a higher accuracy measurement of the azimuth heading. The sample rate of the sensors is such that the sensors maximum error is reduced by the torsional isolator, as the output angular displacements are lower than the input angular displacements.

CROSS-REFERENCE TO RELATED APPLICATION

This application relates to and claims priority to U.S. ProvisionalPatent Application Ser. No. 61/817,945, filed on May 1, 2013, thedisclosure of which is fully incorporated herein by reference, in theentirety.

BACKGROUND OF THE INVENTION

Rotational shock and vibratory input from the drillstring and thevarious components therein limits the accuracy of guidance, such asgyroscopic guidance, for the directional drilling. The existingshock/vibratory absorption equipment fails to substantially preventdegradation of the accuracy of the guidance equipment as the directionaldrilling tool is subjected to shock/vibratory inputs. Additionally,current isolation equipment is incapable of providing a return-to-zeropoint, thereby preventing accurate directional calculations for thegyroscope or directional sonde (i.e. measurement while drilling)

SUMMARY OF THE INVENTION

In many aspects, this invention provides for a torsional isolator fordirectional drilling operations.

In one aspect, the invention provides a torsional isolator for adrillstring, wherein the torsional isolator is positioned in thedrillstring between electronics of the drillstring and a drillbit of thedrillstring. The torsional isolator comprises a first assembly, thefirst assembly having a first end, a second end, at least one annularcavity, and a first spring mount, wherein the first end is joined to theinterconnect opposite of the electronics housing and is proximate thedrillstring electronics. The torsional isolator comprises a secondassembly, the second assembly having a first end, a second end, and asecond spring mount, wherein the second assembly is movably disposedwithin the first assembly and has the second end positioned proximate tothe drillbit, wherein the second spring mount is interiorly positionedwithin one of the at least one annular cavities. The torsional isolatorcomprises at least one bearing, wherein the bearing is movably securedbetween an inner wall of the first assembly and the outer wall of thesecond assembly and provides for rotation therebetween. The torsionalisolator comprises a torsional spring having a first end and a secondend, wherein the first end is affixed to the first spring mount and thesecond end is affixed to the second spring mount. The torsional isolatorcomprises a stop-key having a first key element and a second keyelement, wherein the first key element is positioned on the firstassembly and the second key element positioned on the second assembly,and wherein the first key element and the second key element are capableof preventing a rotation of the second assembly beyond a pre-definedlimit from a static position The torsional isolator comprises a damperelement affixed to the second assembly and positioned proximate theinner wall of the first assembly. The torsional isolator comprises aviscous fluid filling the annular cavity, wherein the viscous fluidprovides viscous damping by having a thin film of viscous fluid adheringto the damper element as the first assembly and second assembly rotaterelative to each other.

In another aspect, the invention provides a torsional isolator for adirectional drilling tool. The directional drilling tool has at least aelectronics housing, at least one interconnect and a drillbit. Theelectronics housing contains at least a drillstring electronics and isjoined with the interconnect, wherein the drillbit is oppositelypositioned from the drillstring electronics on the directional drillingtool. The torsional isolator comprises a first assembly, a secondassembly, at least one bearing, a torsional spring, a stop-key, a damperelement, and a viscous fluid. The first assembly has a first end, asecond end, at least one annular cavity, and a first spring mount,wherein the first end is positioned proximate to the drillbit. Thesecond assembly has a first end, a second end, and a second springmount, wherein the second assembly is movably disposed within the firstassembly and has the second end is joined to the interconnect oppositeof the electronics housing and is proximate the drillstring electronics,wherein the second spring mount is interiorly positioned within one ofthe at least one annular cavities. The bearing is movably securedbetween an inner wall of the first assembly and the outer wall of thesecond assembly and provides for rotation therebetween. The torsionalspring has a first end and a second end, wherein the first end isaffixed to the first spring mount and the second end is affixed to thesecond spring mount. The stop-key has a first key element and a secondkey element, wherein the first key element is positioned on the firstassembly and the second key element is positioned on the secondassembly, and wherein the first key element and the second key elementare capable of preventing a rotation of the second assembly beyond apre-defined limit from a static position. The damper element is affixedto the second assembly and positioned proximate the inner wall of thefirst assembly. The viscous fluid fills the annular cavity, wherein theviscous fluid provides viscous damping by having a thin film of viscousfluid adhering to the damper element as the first assembly and secondassembly rotate relative to each other.

Numerous objects and advantages of the invention will become apparent asthe following detailed description of the preferred embodiments is readin conjunction with the drawings, which illustrate such embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic view of a hydrocarbon recovery systemcomprising a torsional isolator.

FIG. 2 illustrates an oblique view of the torsional isolator of thehydrocarbon recovery system of FIG. 1.

FIG. 3 illustrates an oblique partial view of the torsional isolator ofFIG. 2 and primarily shows a drive shaft of the torsional isolator.

FIG. 4 illustrates an oblique partial view of the torsional isolator ofFIG. 2 and primarily shows a torsional spring and a damper elementassembled to the drive shaft.

FIG. 5 illustrates an oblique partial view of the torsional isolator ofFIG. 2 and primarily shows a first connector of the torsional isolatoras configured for connection to the torsional isolator components ofFIG. 4.

FIG. 6 illustrates an orthogonal bottom end view of the torsionalisolator.

FIG. 7 illustrates a section view of the torsional isolator of FIG. 6taken along section A-A.

FIG. 8 illustrates an enlarged view of an upper portion of the sectionview of FIG. 7.

FIG. 9 illustrates an enlarged view of a lower portion of the sectionview of FIG. 7.

FIG. 10 illustrates an orthogonal upper end view of the torsionalisolator.

FIG. 11 illustrates a section view of the torsional isolator of FIG. 10taken along section B-B.

FIG. 12 illustrates an enlarged view of an upper portion of the sectionview of FIG. 11.

FIG. 13 illustrates an enlarged view of a lower portion of the sectionview of FIG. 11.

FIG. 14 illustrates a section view of the torsional isolator from FIGS.11 and 13 taken along section C-C.

FIG. 15 illustrates a section view of the torsional isolator from FIGS.7 and 9 taken along section D-D.

FIG. 16 illustrates an oblique view of another torsional isolator.

FIG. 17 illustrates a section view of the torsional isolator of FIG. 16.

FIG. 18 illustrates an oblique view of yet another torsional isolator.

FIG. 19 illustrates an orthogonal side view of the torsional isolator ofFIG. 18.

FIG. 20 illustrates an orthogonal upper end view of the torsionalisolator of FIG. 18.

FIG. 21 illustrates a section view of the torsional isolator from FIG.20 taken along section E-E.

FIG. 22 illustrates an enlarged view of an upper portion of the sectionview of FIG. 21.

FIG. 23 illustrates an enlarged view of a lower portion of the sectionview of FIG. 21.

FIG. 24 illustrates a section view of the torsional isolator from FIG.19 taken along section F-F.

FIG. 25 illustrates an enlarged view of an upper portion of the sectionview of FIG. 24.

FIG. 26 illustrates an enlarged view of a lower portion of the sectionview of FIG. 24.

FIG. 27 illustrates a partial cutaway view of the torsional isolator of18.

FIG. 28 illustrates a root mean square performance graph of a torsionalisolator such as the torsional isolator of FIG. 2.

FIG. 29 illustrates a return-to-zero performance graph of a torsionalisolator such as the torsional isolator of FIG. 2.

DETAILED DESCRIPTION

The torsional isolator is shaped to operate in a drillstring associatedwith drilling wells. The torsional isolator has a cylindrical form. Inone embodiment, the torsional isolator is used in directional drillingoperations such as measurement while drilling (MWD).

Referring now to FIG. 1, a schematic view of a hydrocarbon recoverysystem 100 is shown. The hydrocarbon recovery system 100 may be onshoreor offshore. The hydrocarbon recovery system 100 generally comprises adrillstring 102 suspended within a borehole 104. The drillstring 102comprises a drillbit 106 at the lower end of the drillstring 102, amuleshoe or universal bottom hole orienting (UBHO) sub 108 connectedabove the drillbit 106, a bent housing mud motor 110 or other rotarysteerable tool connected between the UBHO sub 108 and the drillbit 106,and a electronics housing 111 or housing that carries electroniccomponents 112. In this embodiment, the hydrocarbon recovery system 100further comprises a torsional isolator 200 configured to providetorsional vibration and/or shock damping as well as torsional and/orangular biasing functionality that tends to maintain and/or returncomponents above and below the isolator to known and/or preset angularorientations relative to each other. The torsional isolator 200 isconnected to the electronics housing 111 via a suitable interconnect113. The torsional isolator 200 is connected to a mule shoe 115 via asuitable interconnect 117. Because the mule shoe 115 and the UBHO sub108 are generally connected via a locating slot and tab configurationand/or some other suitable connection selected to provide a knownorientation between the mule shoe 115 and the UBHO sub 108, the UBHO sub108 and the components connected below the UBHO sub 108 are provided aknown angular orientation relative to the electronics housing 111. Thehydrocarbon recovery system 100 comprises a platform and derrickassembly 114 positioned over the borehole 104 at the surface. Thederrick assembly 114 comprises a rotary table 116 which engages a kelly118 at an upper end of the drillstring 102 to impart rotation to thedrillstring 102. The drillstring 102 is suspended from a hook 120 thatis attached to a traveling block. The drillstring 102 is positionedthrough the kelly 118 and the rotary swivel 122 which permits rotationof the drillstring 102 relative to the hook 120. Additionally oralternatively, a top drive system may be used to impart rotation to thedrillstring 102.

In some cases, the hydrocarbon recovery system 100 further comprisesdrilling fluid 124 which may comprise a water-based mud, an oil-basedmud, a gaseous drilling fluid, water, gas and/or any other suitablefluid for maintaining bore pressure and/or removing cuttings from thearea surrounding the drillbit 106. Some drilling fluid 124 may be storedin a pit 126 and a pumping system 127 may deliver the drilling fluid 124to the interior of the drillstring 102 via a port in the rotary swivel122, causing the drilling fluid 124 to flow downwardly through thedrillstring 102 as indicated by directional arrow 128. The drillingfluid 124 may exit the drillstring 102 via ports in the drillbit 106 andcirculate upwardly through the annulus region between the outside of thedrillstring 102 and the wall of the borehole 104 as indicated bydirectional arrows 130. The drilling fluid 124 lubricates the drillbit106, carries cuttings from the formation up to the surface as it isreturned to the pit 126 for recirculation, and creates a mudcake layer(e.g., filter cake) on the walls of the borehole 104.

The hydrocarbon recovery system 100 further comprises a communicationsrelay 132 and a logging and control processor 134. The communicationsrelay 132 receives information and/or data from sensors, transmitters,and/or receivers located within the electronic components 112 and/orother communicating devices. The information is received by thecommunications relay 132 via a wired communication path through thedrillstring 102 and/or via a wireless communication path. Thecommunications relay 132 transmits the received information and/or datato the logging and control processor 134 and the communications relay132 receives data and/or information from the logging and controlprocessor 134. Upon receiving the data and/or information, thecommunications relay 132 forwards the data and/or information to theappropriate sensor(s), transmitter(s), and/or receiver(s) of theelectronic components 112 and/or other communicating devices. Theelectronic components 112 comprise measuring while drilling (MWD) and/orlogging while drilling (LWD) devices and the electronic components 112may be provided in multiple tools or subs and/or a single tool and/orsub. In alternative embodiments, different conveyance types including,for example, coiled tubing, wireline, wired drill pipe, and/or any othersuitable conveyance type may be utilized. In some embodiments, theabove-described communications comprise mud pulse telemetry in which thedrilling fluid 124 is used as a communication medium.

Referring now to FIG. 2, the torsional isolator 200 of hydrocarbonrecovery system 100 is shown in greater detail. Specifically referringto FIGS. 2-5, the torsional isolator 200 includes a barrel 202longitudinally connected between a first connector 204 and a secondconnector 206. The first connector 204 includes a female receptacle forreceiving and connecting to other drillstring 102 components. The secondconnector 206 includes a male portion for insertion to and connecting toother drillstring 102 components. The torsional isolator 200 isconfigured so that the first connector 204 is an upper or higher locatedconnector as compared to the second connector 206 that is locatedrelatively lower in the drillstring 102. The torsional isolator 200 isconfigured to damp angular rotational energy transmitted between thefirst connector 204 and the second connector 206. The torsional isolator200 is also configured to provide rotational and/or angular biasingforces between the first connector 204 and the second connector 206 sothat the torsional isolator 200 tends to maintain or return the firstconnector 204 to a preset and/or known relative angular orientation thesecond connector 206 is maintained when rotational forces of hydrocarbonrecovery system 100 permit. The torsional isolator 200 has a centrallongitudinal axis 208. The above-described rotational and/or angularbiasing forces and relative rotational and/or angular orientations arerelative to rotation about the central longitudinal axis 208. Theangular damping functionality of the torsional isolator 200 isaccomplished by shearing fluids 210 within the torsional isolator 200.The angular biasing force and/or angular orientation returnfunctionality of the torsional isolator 200 is accomplished in part bytransmitting angular forces through a torsional spring 212 configured toallow loading of the spring in both rotational directions about thecentral longitudinal axis 208.

Referring now to FIGS. 2-15, the torsional isolator 200 includes a firstassembly 214 that is generally torsionally rigid and a second assembly216 that is also generally torsionally rigid. Rotation of the firstassembly 214 relative to the second assembly 216 is damped by shearingthe fluids 210. Relative angular displacements of the first assembly 214relative to the second assembly 216 are resisted and/or decreased by thetorsional spring 212. The first assembly 214 includes the barrel 202,the first connector 204, a thrust insert 218, and a centering insert220. The first connector 204 is partially received within the barrel 202and is joined to the barrel 202 via a sealed and threaded connection.The thrust insert 218 is received within and joined to the lower end ofthe barrel 202 via a sealed and threaded connection. The centeringinsert 220 is received within and joined to the lower end of the thrustinsert 218 via a sealed and threaded connection. The second assembly 216includes the second connector 206, a drive shaft 222, and a damperelement 224. The drive shaft 222 is connected to the second connector206 via a threaded connection and is further captured relative to thesecond connector 206 using slotted spring pins 226 inserted into holesof the second connector 206 and concavities of the drive shaft 222. Thedamper element 224 is connected to the upper end of the drive shaft 222via a Woodruff key 228 captured between a recess 230 of the drive shaft222 and channel 232 of the damper element 224.

The drive shaft 222 is received through central passages of thecentering insert 220, the thrust insert 218, and the torsional spring212. The upper end of the drive shaft 222 is received within a lowercavity 234 of the first connector 204. Needle bearings 236 are disposedin the lower central cavity 234 between the first connector 204 and thedrive shaft 222. The needle bearings 236 serve to maintain a coaxialalignment between the first assembly 214 and the second assembly 216.Radial bearings 238 or ball bearings are captured between the thrustinsert 218, the centering insert 220, and the drive shaft 222 tomaintain a coaxial alignment between the first assembly 214 and thesecond assembly 216. Thrust bearings 240 are provided between a shoulder242 of the drive shaft 222 and adjacent portions of the thrust insert218 and the thrust bearings 240 are captured by connecting a bearing nut244 to an upper interior portion of the thrust insert 218. The thrustbearings 240 provide a strong axial load transfer path so that largecompressive or tensile loads are fully transmitted through the torsionalisolator 200 even while the torsional isolator 200 serves to reducesystem energy associated with twisting the torsional isolator 200 aboutthe central longitudinal axis 208. The thrust bearings 240 areparticularly useful in transferring axial forces associated withdrilling and fishing out drillstring 102 components.

In this embodiment, the torsional spring 212 is joined between the firstassembly 214 and the second assembly 216. The torsional spring 212includes a first spring mount 246 and a second spring mount 248 joinedtogether by a helical winding 250 that wraps around the drive shaft 222.The first spring mount 246 is connected to the second assembly 216.Referring to FIGS. 4 and 14, the first spring mount 246 includes aportion of a cylindrical half ring shape and a lower end of the damperelement 224 includes a generally complementary cylindrical half ringshape. The half ring shapes are joined together around the drive shaft222 by threaded bolts received in bolt holes 252. In this way, the firstspring mount 246 of the torsion spring 212 is rotationally locked withthe second assembly 216. The second spring mount 248 is connected to thefirst assembly 214. The second spring mount 248 includes a cylindricalring shape that is received within and adjacent to the inner wall of thebarrel 202. The cylindrical ring shape and the barrel 202 are joinedtogether by threaded bolts received in bolt holes 254. In this way, thesecond spring mount 248 of the torsion spring 212 is rotationally lockedwith the first assembly 214. Accordingly, differentials in angularrotation between the first assembly 214 and the second assembly 216result in winding or unwinding the torsional spring 212 from a default,zero, and/or resting position. When the external rotational forces aresufficiently reduced, the torsional spring 212 will return the firstconnector 204 and the second connector 206 to the initial, default,zero, and/or resting relative positions that is selected to additionallyreturn the rotationally sensitive electronics 212 to a known angularlocation and/or aziumuth. This behavior is also referred to as areturn-to-zero behavior or functionality.

In this embodiment, the damper element 224 includes a thin tube 256 atthe upper end of the damper element 224 and the first connector 204includes a cylindrical protrusion 258 at the lower end of the firstconnector 204. When the torsional isolator 200 is assembled, the damperelement 224 is radially captured between the cylindrical protrusion 258and the interior wall of the barrel 202. In this embodiment, fluid 210is provided to the annular spaces between the thin tube 256 and thecylindrical protrusion 258. Fluid 210 is also provided to the annularspaces between the thin tube 256 and the barrel 202. Accordingly,differentials in angular rotation between the first assembly 214 and thesecond assembly 216 result in shearing of the fluid 212, a process thatconsumes rotational energy and thereby dampens the torsional isolator200 response. This behavior is also referred to as angular or torsionaldamping. In this embodiment, the fluid 210 is introduced into theisolator 200 via a fill port 260 that extends centrally andlongitudinally from the first connector 204 to spaces in fluidcommunication with the annular spaces adjacent the thin tube 256. A sealscrew 262 is used to seal the fill port 260.

During operations of the hydrocarbon recovery system 100 and thetorsional isolator 200, the second assembly 216 is subjected tosubstantial vibration and shock as the vibration and shock aretransmitted from the drillbit 106 and/or other drillstring 102components. The amplitude of angular or torsional vibration, shock,and/or displacement transmitted from the first assembly to thedrillstring 102 is reduced as a function of the resistance of thetorsional spring 212 and/or the damper element 224 shearing the fluid210. In an alternative embodiment (not shown), the positioning of thefirst assembly 214 and the second assembly 216 on the drillstring 102may be flipped such that the first assembly 214 is positioned nearer thedrillbit 106 than the second assembly 216.

Described another way, the torsional isolator 200 has at least threetypes and/or sets of interfaces between the first assembly 214 and thesecond assembly 216. A first set of interfaces are the above-describedbearing interfaces. While the types of bearings are described above asincluding radial bearings, thrust bearings, and needle bearings, anytype of bearing capable of being movably secured between an innercylindrical wall and an outer cylindrical wall and providing forrotation between the first assembly 214 and the second assembly 216 arecontemplated by this disclosure. Preferably, the bearings minimizefriction between the first assembly 214 and the second assembly 216. Thevalue of reducing the friction is to transmit as little of the shock andvibration as possible from the input side of the damper to an outputside, namely, the lower end of the second assembly 216 to the upper endof the first assembly 214. Lower friction also allows the torsionalisolator to return the upper and lower ends of the torsional isolator200 to zero or neutral positions, which are associated with a trueazimuth heading of a component of the electronics 212, namely, adirectional assembly.

The second type of interface is the torsional spring 222. The torsionalisolator has a static position when the tool is at rest. The positioningof the torsional spring 222 creates a centering force for counteractingthe rotational forces of second assembly 216. The result is that thefirst assembly 214 returns to an original position associated with thestatic position so that as the second assembly 216 is rotated, the firstassembly 214 will eventually return to its original static positionrelative to the second assembly 216. The torsional spring 222 ensuresthe first assembly 214 returns to the same static position, alsoreferred to as the neutral or zero point rotationally with respect tothe second assembly 216. This requirement provides for the electronics212 to be able to measure a tool face. The tool face is defined as thetrue azimuth heading of a directional drilling assembly.

Referring now to FIG. 15, a stop-key 262 is comprised of a first keyelement 264 and a second key element 266. As shown in FIG. 15, the firstkey element 264 is positioned on the first assembly 214 and the secondkey element 266 is positioned on the second assembly 216. The first keyelement 264 and the second key element 266 are capable of preventing arotation of the second assembly 216 beyond a pre-defined angular limitfrom a static position. The stop-key 262 and/or the placement of thetorsional spring 212 at the first spring 246 mount prevents angularmotions of the second assembly 216 beyond a predefined limit. In oneembodiment, a tab (not shown) and stop-key 262 are used with thetorsional spring 212 to prevent motion beyond the predefined limit. Inone embodiment, the predefined limit is about ±120 degrees. In oneembodiment, when the second assembly 216 rotates up to about ±120degrees, the second spring mount 248 functions as a hard stop andcontacts a stop-key mounted to the second assembly, thereby preventingany additional rotation. Elastomeric bumpers 268 are provided to softenthe contact between the first key element 264 and the second key element266.

The third type of interface is the damper element 224 which isconfigured to rotate relative to adjacent components in a manner thatshears fluid 210. Each annular cavity, as well as the other cavities,within the torsional isolator is preferably filled with a viscous fluidsuch as silicone. The viscous fluid is selected for a particularapplication based upon the viscosity and the desired damping properties.By way of a non-limiting example, the viscosity of the vicious fluid isbetween about 2,000 centistokes (cSt) to about 60,000 cSt. In theembodiment using silicone fluid, the viscous fluid has a viscosity ofabout 20,000 cSt. As the first assembly 214 and the second assembly 216rotate relative to each other, a thin film of viscous fluid adheres tothe opposing sides of the damper element 224. The viscous fluid 210 issubjected to shear forces that result in viscous damping of rotationalforces. This viscous damping facilitates the return of the torsionalisolator 200 to a zero position by using the torsional spring 222.

In this embodiment, the torsional spring 222 is a wire wound spring or amachined spring. The torsional spring 222 works in torsionally and/orangularly alternating directions and allows for plus/minus motion with asingle component. This plus/minus motion biases the torsional isolatorto the zero position. This is similar to the embodiment discussedherein. In an alternate embodiment, the torsional spring 222 is awire-coil spring (not shown). In another alternate embodiment, thetorsional spring 222 is a two-wire-coil spring (not shown) working inopposing directions, thereby enabling a positive preload to the zeroposition. In yet another alternate embodiment, a rubber tubeformconfiguration (not shown) functions as the torsional spring 222 and iscombined with one or more of the previously identified embodiments.

In addition to the foregoing embodiments, the torsional isolator 200allows the electronics 212 to angularly oscillate at a slower rotationalvelocity than the data acquisition rate of associated sensors, such thatthe sensors are recording an average value of the azimuth heading. As aresult, the average value of the azimuth heading is more accurate thantaking an instantaneous reading at the wrong heading as would be thecase when electronics and/or sensors are more rigidly coupled to thesource of vibration and/or oscillation of the drillstring 102, such as,in a case where no torsional isolator 200 is utilized.

Referring now to FIGS. 16 and 17, another embodiment of a torsionalisolator 300 is shown. The torsional isolator 300 is substantiallysimilar to the torsional isolator 200 but the torsional isolator 300includes no stop-key substantially similar to stop-key 262. Otherwise,the components and features referenced by 304, 314, 302, 354, 318, 320,316, 306, 308, 362, 360, 310, 334, 336, 324, 346, 312, 348, 350, 322,344, 340, 342, 328, 320, 356, and 338 represent components and featuressubstantially similar to the components and features of torsionalisolator 200 referenced by referenced by 204, 214, 202, 254, 218, 220,216, 206, 208, 262, 260, 210, 234, 236, 224, 246, 212, 248, 250, 222,244, 240, 242, 228, 220, 256, and 238, respectively.

Referring now to FIGS. 18-27, the torsional isolator 400 includes afirst assembly 414 that is generally torsionally rigid and a secondassembly 416 that is also generally torsionally rigid. Rotation of thefirst assembly 414 relative to the second assembly 416 is damped byshearing the fluids 410. Relative angular displacements of the firstassembly 414 relative to the second assembly 416 are resisted and/ordecreased by the torsional spring 412. The first assembly 414 includesthe barrel 402, the first connector 404, a thrust insert 418, and acentering insert 420. The first connector 404 is partially receivedwithin the barrel 402 and is joined to the barrel 402 via a sealed andthreaded connection. The thrust insert 418 is received within and joinedto the lower end of the barrel 402 via a sealed and threaded connection.The centering insert 420 is received within and joined to the lower endof the thrust insert 418 via a sealed and threaded connection. Thesecond assembly 416 includes the second connector 406, a drive shaft422, and a damper element 424. The drive shaft 422 is connected to thesecond connector 406 via a threaded connection and is further capturedrelative to the second connector 406 using slotted spring pins 426inserted into holes of the second connector 406 and concavities of thedrive shaft 422. The damper element 424 is connected to the upper end ofthe drive shaft 422 via a Woodruff key 428 captured between a recess 430of the drive shaft 422 and channel 432 of the damper element 424.

The drive shaft 422 is received through central passages of thecentering insert 420, the thrust insert 418, and the torsional spring412. The upper end of the drive shaft 422 is received within a lowercavity 434 of the first connector 404. Needle bearings 436 are disposedin the lower central cavity 434 between the first connector 404 and thedrive shaft 422. The needle bearings 436 serve to maintain a coaxialalignment between the first assembly 414 and the second assembly 416.Radial bearings 438 or ball bearings are captured between the thrustinsert 418, the centering insert 420, and the drive shaft 422 tomaintain a coaxial alignment between the first assembly 414 and thesecond assembly 416. Thrust bearings 440 are provided between a shoulder442 of the drive shaft 422 and adjacent portions of the thrust insert418 and the thrust bearings 440 are captured by connecting a bearing nut444 to an upper interior portion of the thrust insert 418. The thrustbearings 440 provide a strong axial load transfer path so that largecompressive or tensile loads are fully transmitted through the torsionalisolator 400 even while the torsional isolator 400 serves to reducesystem energy associated with twisting the torsional isolator 400 aboutthe central longitudinal axis 408. The thrust bearings 440 areparticularly useful in transferring axial forces associated withdrilling and fishing out drillstring 102 components.

In this embodiment, the torsional spring 412 is joined between the firstassembly 414 and the second assembly 416. The torsional spring 412includes a first spring mount 446 and a second spring mount 448 joinedtogether by a helical winding 450 that wraps around the drive shaft 422.The first spring mount 446 is connected to the second assembly 416 bythreaded bolts. In this way, the first spring mount 446 of the torsionspring 412 is rotationally locked with the second assembly 416. Thesecond spring mount 448 is connected to the first assembly 414. Thesecond spring mount 448 includes a cylindrical ring shape that isreceived within and adjacent to the inner wall of the barrel 402. Thecylindrical ring shape and the barrel 402 are joined together bythreaded bolts received in bolt holes 454. In this way, the secondspring mount 448 of the torsion spring 412 is rotationally locked withthe first assembly 414. Accordingly, differentials in angular rotationbetween the first assembly 414 and the second assembly 416 result inwinding or unwinding the torsional spring 412 from a default, zero,and/or resting position. When the external rotational forces aresufficiently reduced, the torsional spring 412 will return the firstconnector 404 and the second connector 406 to the initial, default,zero, and/or resting relative positions that is selected to additionallyreturn the rotationally sensitive electronics 412 to a known angularlocation and/or aziumuth. This behavior is also referred to as areturn-to-zero behavior or functionality.

In this embodiment, the damper element 424 includes a thin tube 256 atthe upper end of the damper element 424 and the first connector 404includes a cylindrical protrusion 458 at the lower end of the firstconnector 404. When the torsional isolator 400 is assembled, the damperelement 424 is radially captured between the cylindrical protrusion 458and the interior wall of the barrel 402. In this embodiment, fluid 410is provided to the annular spaces between the thin tube 456 and thecylindrical protrusion 458. Fluid 410 is also provided to the annularspaces between the thin tube 456 and the barrel 402. Accordingly,differentials in angular rotation between the first assembly 414 and thesecond assembly 416 result in shearing of the fluid 410, a process thatconsumes rotational energy and thereby dampens the torsional isolator400 response. This behavior is also referred to as angular or torsionaldamping. In this embodiment, the fluid 410 is introduced into theisolator 400 via a fill port 460 that extends centrally andlongitudinally from the first connector 404 to spaces in fluidcommunication with the annular spaces adjacent the thin tube 456. A sealscrew 462 is used to seal the fill port 460.

During operations of the hydrocarbon recovery system 100 and thetorsional isolator 400, the second assembly 416 is subjected tosubstantial vibration and shock as the vibration and shock aretransmitted from the drillbit 106 and/or other drillstring 102components. The amplitude of angular or torsional vibration, shock,and/or displacement transmitted from the first assembly to thedrillstring 102 is reduced as a function of the resistance of thetorsional spring 412 and/or the damper element 424 shearing the fluid410. In an alternative embodiment (not shown), the positioning of thefirst assembly 414 and the second assembly 416 on the drillstring 102may be flipped such that the first assembly 414 is positioned nearer thedrillbit 106 than the second assembly 416.

Described another way, the torsional isolator 400 has at least threetypes and/or sets of interfaces between the first assembly 414 and thesecond assembly 416. A first set of interfaces are the above-describedbearing interfaces. While the types of bearings are described above asincluding radial bearings, thrust bearings, and needle bearings, anytype of bearing capable of being movably secured between an innercylindrical wall and an outer cylindrical wall and providing forrotation between the first assembly 414 and the second assembly 416 arecontemplated by this disclosure. Preferably, the bearings minimizefriction between the first assembly 414 and the second assembly 416. Thevalue of reducing the friction is to transmit as little of the shock andvibration as possible from the input side of the damper to an outputside, namely, the lower end of the second assembly 416 to the upper endof the first assembly 414. Lower friction also allows the torsionalisolator to return the upper and lower ends of the torsional isolator400 to zero or neutral positions, which are associated with a trueazimuth heading of a component of the electronics 412, namely, adirectional assembly.

The second type of interface is the torsional spring 422. The torsionalisolator has a static position when the tool is at rest. The positioningof the torsional spring 422 creates a centering force for counteractingthe rotational forces of second assembly 416. The result is that thefirst assembly 414 returns to an original position associated with thestatic position so that as the second assembly 416 is rotated, the firstassembly 414 will eventually return to its original static positionrelative to the second assembly 416. The torsional spring 422 ensuresthe first assembly 414 returns to the same static position, alsoreferred to as the neutral or zero point rotationally with respect tothe second assembly 416. This requirement provides for the electronics412 to be able to measure a tool face. The tool face is defined as thetrue azimuth heading of a directional drilling assembly. A stop-key 462substantially similar to stop-key 262 is provided. The stop-key 462and/or the placement of the torsional spring 412 at the first springmount 446 prevents angular motions of the second assembly 416 beyond apredefined limit. In one embodiment, a tab (not shown) and stop-key 462are used with the torsional spring 412 to prevent motion beyond thepredefined limit In one embodiment, the predefined limit is about ±120degrees. In one embodiment, when the second assembly 416 rotates up toabout ±120 degrees, the second spring mount 448 functions as a hard stopand contacts a stop-key mounted to the second assembly, therebypreventing any additional rotation.

Referring now to FIG. 27, a first difference between torsional isolator400 and torsional isolators 200,300 is that the lower end of the damperelement 424 is located relatively higher and is bolted to a longitudinalspacer 425 by threaded bolts. Referring now to FIGS. 21-26 Anotherdifference between torsional isolator 400 and torsional isolators200,300 is that the longitudinal length of the thrust insert 418 issignificantly longer, thereby lengthening an annular space within thethrust insert 418 as well as lengthening the overall longitudinal lengthof the torsional isolator 400.

One or more of the torsional isolators 200, 300, 400 and/or alternativeembodiments disclosed herein may comprise a spring rate (K) of 0.6in*lb/degrees and a damping coefficient (C) of 0.05 in*lb*sec/degrees ata design frequency of about 5-7 Hz and a design amplitude of about 10-15degrees for hydrocarbon recovery systems utilizing a single torsionalisolator. One or more of the torsional isolators 200, 300, 400 and/oralternative embodiments disclosed herein comprise a spring rate (K) of0.3 in*lb/degrees and a damping coefficient (C) of 0.03in*lb*sec/degrees at a design frequency of about 5-7 Hz and a designamplitude of about 10-15 degrees for hydrocarbon recovery systemsutilizing two torsional isolators. One or more of the torsionalisolators 200, 300, 400 and/or alternative embodiments disclosed hereinmay alternatively comprise a spring rate (K) of 0.7 in*lb/degrees(static) and 0.4+/−0.1 in*lb/degrees (dynamic) and a damping coefficient(C) of 0.06+/−0.01 in*lb*sec/degrees at a design frequency of about0.1-10 Hz and a design amplitude of about 0.5-14.7 degrees forhydrocarbon recovery systems utilizing a single torsional isolator.

Referring now to FIG. 28, a graph of degrees of rotation versus time isprovided that compares a larger input angular drive envelope to asmaller output angular driven envelope. The graphed data is useful forcalculating a root mean square (RMS) input value of 0.70 degrees and aRMS output value of 0.47 degrees which is approximately a 33% reductionin angular rotation. In some embodiments, an RMS reduction of up toabout 50%.

In some embodiments, peak amplitude angular displacement reductions ofabout 20-60% are contemplated. In some embodiments, the generaloperating conditions of a torsional isolator disclosed herein includeoperating pressures of about 20,000 psi, temperatures of about 350degrees Fahrenheit, and fishing loads of about 20,000 lb.

Referring now to FIG. 29, a graph of degrees of rotation versus time isprovided that demonstrates that the angular location of the torsionalisolators disclosed herein may, as viewed on the graph, remain centeredon the vibratory input while drilling is taking place. Once drillingand/or vibratory input ceases, the torsional isolators angularly returnto zero locations and/or orientations.

In some embodiments, fluids such as fluid 210 may leak from thetorsional isolators disclosed herein as a result of the fluid expandingto due increased operation temperatures as compared to the temperaturesat which the fluid was inserted into the torsional isolators. In someembodiments, it is contemplated that the torsional isolators disclosedherein be refilled with fluid after being fished out and/or after a setnumber of hours of operation, such as 250 hours.

In some embodiments, the phrase “an upper end” refers to a first end andthe phrase “a lower end” refers to as a second end. It will beappreciated that any of the torsional isolators 300, 400, and/oralternative embodiments of torsional isolators disclosed herein may beutilized in place of and/or in addition to the torsional isolator 200 ofthe hydrocarbon recovery system 100. Further, multiple torsionalisolators of the same or different type may be utilized in a hydrocarbonrecovery system 100 or other drilling and/or directional drillingsystem.

Other embodiments of the current invention will be apparent to thoseskilled in the art from a consideration of this specification orpractice of the invention disclosed herein. Thus, the foregoingspecification is considered merely exemplary of the current inventionwith the true scope thereof being defined by the following claims.

What is claimed is:
 1. A torsional isolator for a drillstring, whereinthe torsional isolator is positioned in the drillstring betweenelectronics of the drillstring and a drillbit of the drillstring, thetorsional isolator comprising: a first assembly, the first assemblyhaving a first end, a second end, at least one annular cavity, and afirst spring mount, wherein the first end is joined to the interconnectopposite of the electronics housing and is proximate the drillstringelectronics; a second assembly, the second assembly having a first end,a second end, and a second spring mount, wherein the second assembly ismovably disposed within the first assembly and has the second endpositioned proximate to the drillbit, wherein the second spring mount isinteriorly positioned within one of the at least one annular cavities;at least one bearing, wherein the bearing is movably secured between aninner wall of the first assembly and an outer wall of the secondassembly and provides for rotation therebetween; a torsional springhaving a first end and a second end, wherein the first end is affixed tothe first spring mount and the second end is affixed to the secondspring mount; a stop-key having a first key element and a second keyelement, wherein the first key element is positioned on the firstassembly and the second key element positioned on the second assembly,and wherein the first key element and the second key element are capableof preventing a rotation of the second assembly beyond a pre-definedlimit from a static position; a damper element affixed to the secondassembly and positioned proximate the inner wall of the first assembly;and a viscous fluid filling the annular cavity, wherein the viscousfluid provides viscous damping by having a thin film of viscous fluidadhering to the damper element as the first assembly and second assemblyrotate relative to each other.
 2. The torsional isolator of claim 1,wherein the predefined limit is ±120 degrees.
 3. The torsional isolatorof claim 1, further comprising at least three bearings.
 4. The torsionalisolator of claim 3, wherein at least one of the bearings is a radialbearing.
 5. The torsional isolator of claim 3, wherein at least one ofthe bearings is a thrust bearing.
 6. The torsional isolator of claim 3,wherein at least one of the bearings is a needle bearing.
 7. A torsionalisolator for a directional drilling tool having at least a electronicshousing, at least one interconnect and a drillbit, the electronicshousing contains at least a drillstring electronics and is joined withthe interconnect, wherein the drillbit is oppositely positioned from thedrillstring electronics on the directional drilling tool, the torsionalisolator comprising: a first assembly, the first assembly having a firstend, a second end, at least one annular cavity, and a first springmount, wherein the first end is positioned proximate to the drillbit; asecond assembly, the second assembly having a first end, a second end,and a second spring mount, wherein the second assembly is movablydisposed within the first assembly and the second end is joined to theinterconnect opposite of the electronics housing and is proximate thedrillstring electronics, wherein the second spring mount is interiorlypositioned within one of the at least one annular cavities; at least onebearing, wherein the bearing is movably secured between an inner wall ofthe first assembly and an outer wall of the second assembly and providesfor rotation therebetween; a torsional spring having a first end and asecond end, wherein the first end is affixed to the first spring mountand the second end is affixed to the second spring mount; a stop-keyhaving a first key element and a second key element, wherein the firstkey element is positioned on the first assembly and the second keyelement positioned on the second assembly, and wherein the first keyelement and the second key element are capable of preventing a rotationof the second assembly beyond a pre-defined limit from a staticposition; a damper element affixed to the second assembly and positionedproximate the inner wall of the first assembly; and a viscous fluidfilling the annular cavity, wherein the viscous fluid provides viscousdamping by having a thin film of viscous fluid adhering to the damperelement as the first assembly and second assembly rotate relative toeach other.
 8. The torsional isolator of claim 7, wherein the predefinedlimit is ±120 degrees.
 9. The torsional isolator of claim 7, furthercomprising at least three bearings.
 10. The torsional isolator of claim9, wherein at least one of the bearings is a radial bearing.
 11. Thetorsional isolator of claim 9, wherein at least one of the bearings is athrust bearing.
 12. The torsional isolator of claim 9, wherein at leastone of the bearings is a needle bearing.
 13. A torsional isolator for adrillstring, wherein the torsional isolator is positioned in thedrillstring between electronics of the drillstring and a drillbit of thedrillstring, the torsional isolator comprising: a first assembly, thefirst assembly having a first end, a second end, at least one annularcavity, and a first spring mount, wherein the first end is joined to theinterconnect opposite of the electronics housing and is proximate thedrillstring electronics; a second assembly, the second assembly having afirst end, a second end, and a second spring mount, wherein the secondassembly is movably disposed within the first assembly and has thesecond end positioned proximate to the drillbit, wherein the secondspring mount is interiorly positioned within one of the at least oneannular cavities; at least one bearing, wherein the bearing is movablysecured between an inner wall of the first assembly and an outer wall ofthe second assembly and provides for rotation therebetween; a torsionalspring having a first end and a second end, wherein the first end isaffixed to the first spring mount and the second end is affixed to thesecond spring mount; a damper element affixed to the second assembly andpositioned proximate the inner wall of the first assembly; and a viscousfluid filling the annular cavity, wherein the viscous fluid providesviscous damping by having a thin film of viscous fluid adhering to thedamper element as the first assembly and second assembly rotate relativeto each other.